Waveguide coupler

ABSTRACT

Conventionally, waveguide terminals formed in a plurality of dielectric substrates are joined together by mounting the dielectric substrates on carriers and fastening them to a waveguide adapter with screws. In the present invention, ot reduce cost and improve machinability, a plurality of solders  7  are disposed around the waveguide terminal  2   b  formed in one dielectric substrate  1   b , and the other dielectric substrate  1   a  having the waveguide terminal  2   a  is placed across the solders  7  to thereby connect the waveguide terminals by soldering.

BACKGROUND OF THE INVENTION

[0001] 1. Filed of the Invention

[0002] The present invention relates to a waveguide coupler of waveguideterminals formed in dielectric substrates used in conjunction with ahigh frequency band, such as microwave or millimeter-wave band.

[0003] 2. Description of the Related Art

[0004]FIG. 1 is an exploded perspective view showing a configuration forcoupling waveguide terminals formed in dielectric substrates by aconventional waveguide coupler. FIG. 2 is a side view when the waveguideterminals are joined together by a conventional waveguide coupler. Inthese figures, 1 a and 1 b indicate dielectric substrates, 2 a, 2 b, 2c, 2 d, and 2 e indicate waveguide terminals, 3 a and 3 b indicatecarriers, 4 indicates a waveguide adapter, 5 indicates a screw holeformed in the waveguide adapter, and 6 indicates a screw.

[0005] An example of such a conventional waveguide coupler will bedescribed. In FIGS. 1 and 2, the dielectric substrates 1 a and 1 bhaving the waveguide terminals 2 a and 2 e formed therein are bonded tothe carriers 3 a and 3 b, respectively, having the waveguide terminals 2b, and 2 d with an adhesive or by soldering or brazing. The twodielectric substrates bonded to the carries are aligned with thewaveguide adapter 4 so that the positions of the waveguide terminals 2b, 2 c, and 2 d coincide with each other, and then fastened at the screwholes 5 with the screws 6. Thus, the conventional dielectric substrateshaving the waveguide terminals formed therein are connected togetherwith screws via carriers, a waveguide adapter, and so on.

[0006] A transmitter-receiver circuit, for example, is provided on thedielectric substrates 1 a, 1 b, for converting high frequency radiowaves transmitted through a waveguide to electrical signals transmittingthrough a conductor, and vice versa. The transmitter circuit generates ahigh frequency signal in response to a signal entered externally to thedielectric substrate and supplies it to the carriers 3 a, 3 b side fromthe waveguide terminals 2 a, 2 e. On the other hand, the receivercircuit converts the high frequency signal entered from the carriers 3a, 3 b side to the waveguide terminals 2 a, 2 b to an electrical signaland supplies it externally, for example.

[0007] As described above, because conventional waveguide couplers useexpensive carriers and waveguide adapter and are fastened with screws,efforts to reduce their cost have failed, and they continue to sufferfrom degraded machinability. Moreover, because the carriers and thewaveguide adapter generally have different coefficients of thermalexpansion, when the dielectric substrates are connected and fixed on thecarriers and the waveguide adapter using an adhesive, there is a risk ofablation of the adhesive surface or fracture of associated members.Further, the wiring for input/output of electrical signals to/from thecircuit on the dielectric substrate is formed by connecting wirematerials onto the top surface of the dielectric substrate by bonding,for example, which complicates the manufacturing process.

SUMMARY OF THE INVENTION

[0008] The present invention is made to solve the above problems.Therefore, an object of the present invention is to provide a waveguidecoupler which is capable of simplifying the process, such as the processof connecting waveguide terminals of dielectric substrates having a highfrequency circuit formed thereon, while reducing the cost of thewaveguide coupler.

[0009] In a first aspect of the present invention, a waveguide couplerfor connecting between rectangular waveguide terminals formed in twodielectric substrates arranged opposite to each other is provided. Eachdielectric substrate includes a contact region which conductselectricity to a grounded conductor of the waveguide terminal. Onecontact region is arranged to surround the waveguide terminal at aposition opposite to the other contact region when both waveguideterminals are connected together. Both dielectric substrates are joinedwith an electrically conductive joint member disposed between theopposing contact regions.

[0010] With the present invention, the process of connecting between thewaveguide terminals, which has conventionally been manually fastenedwith screws, can be simplified. Moreover, it is possible to reduce thecost of the coupler, because there is no need to use expensive parts,such as a waveguide adapter and carriers.

[0011] In a second aspect of the present invention, a plurality ofelectrically conductive joint members are arranged to surround awaveguide terminal of an individual dielectric substrate. Bothdielectric substrates are joined by the multiple conductive jointmembers which are sandwiched between the waveguide terminals of bothdielectric substrates. This prevents the degradation of the transfercharacteristic of high frequency waves at the waveguide coupler, absorbsa difference between, for example, the coefficients of thermal expansionof both dielectric substrates. Moreover, because stress in the firstdielectric substrate as a result of distortion due to thermal expansionor the like of the second dielectric substrate is unlikely to result,resulting cracks or other failures or defects in the first dielectricsubstrate can be prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is an exploded perspective view of a conventional waveguidecoupler;

[0013]FIG. 2 is a vertical section of the conventional waveguidecoupler;

[0014]FIG. 3A is an exploded perspective view of a waveguide coupleraccording to an Embodiment 1;

[0015]FIG. 3B is a vertical section of the waveguide coupler accordingto Embodiment 1;

[0016]FIG. 4 is an exploded perspective view of a waveguide coupleraccording to an Embodiment 2;

[0017]FIG. 5A is a top view of a dielectric substrate which forms awaveguide coupler according to Embodiment 2, wherein a rectangular holeis formed as a waveguide terminal;

[0018]FIG. 5B is a vertical section of the waveguide coupler using thedielectric substrate shown in FIG. 5A;

[0019]FIG. 6A is a top view of a dielectric substrate which formsanother waveguide coupler according to Embodiment 2, wherein a waveguideterminal is formed by providing through holes in a rectangular shape;

[0020]FIG. 6B is a vertical section of the waveguide coupler using thedielectric substrate shown in FIG. 6A;

[0021]FIG. 7 is a vertical section of a model of a high frequency deviceusing the waveguide coupler according to the present invention;

[0022]FIG. 8A is a top view of another dielectric substrate which formsa waveguide coupler according to an Embodiment 3, wherein a rectangularhole is formed as a waveguide terminal;

[0023]FIG. 8B is a top view of a still another dielectric substratewhich forms the waveguide coupler according to Embodiment 3, wherein awaveguide terminal is formed by providing through holes in a rectangularshape;

[0024]FIG. 9 is a graph showing the characteristic of the waveguidecoupler according to Embodiment 3;

[0025]FIG. 10A is a top view of a dielectric substrate according to anEmbodiment 4;

[0026]FIG. 10B is a vertical section of a single-layered dielectricsubstrate according to Embodiment 4;

[0027]FIG. 10C is a vertical section of a multi-layered dielectricsubstrate according to Embodiment 4;

[0028]FIG. 11A is a top view of a dielectric substrate according to anEmbodiment 5;

[0029]FIG. 11B is a vertical section of the dielectric substrateaccording to Embodiment 5;

[0030]FIG. 12A is a top view of a dielectric substrate according to anEmbodiment 6;

[0031]FIG. 12B is a vertical section of a single-layered dielectricsubstrate according to Embodiment 6;

[0032]FIG. 12C is a vertical section of a multi-layered dielectricsubstrate according to Embodiment 6;

[0033]FIG. 13A is a top view of a dielectric substrate according to anEmbodiment 7;

[0034]FIG. 13B is a vertical section of a single-layered dielectricsubstrate according to Embodiment 7;

[0035]FIG. 13C is a vertical section of a multi-layered dielectricsubstrate according to Embodiment 7;

[0036]FIG. 14A is a top view of a dielectric substrate according to anEmbodiment 8;

[0037]FIG. 14B is a vertical section of the dielectric substrateaccording to Embodiment 8;

[0038]FIG. 15 is a graph showing the characteristic of the waveguidecoupler according to Embodiment 8;

[0039]FIG. 16A is a top view of a dielectric substrate according to anEmbodiment 9;

[0040]FIG. 16B is a vertical section of the dielectric substrateaccording to Embodiment 9;

[0041]FIG. 17 is a graph showing the characteristic of the waveguidecoupler according to Embodiment 9;

[0042]FIG. 18A is a top view of a dielectric substrate according to anEmbodiment 10;

[0043]FIG. 18B is a vertical section of the dielectric substrateaccording to Embodiment 10;

[0044]FIG. 19A is a top view of the first dielectric substrate whichforms a waveguide coupler according to an Embodiment 11;

[0045]FIG. 19B is a vertical section of the waveguide coupler accordingto Embodiment 11;

[0046]FIG. 19C is a top view of the second dielectric substrate whichforms the waveguide coupler according to Embodiment 11;

[0047]FIG. 20A is an exploded perspective view of a waveguide coupleraccording to an Embodiment 12;

[0048]FIG. 20B is a vertical section of the waveguide coupler accordingto Embodiment 12;

[0049]FIG. 21A is an exploded perspective view of a waveguide coupleraccording to an Embodiment 13;

[0050]FIG. 21B is a vertical section of the waveguide coupler accordingto Embodiment 13; and

[0051]FIG. 22 is a vertical section of a modified example of thewaveguide coupler according to the Embodiment 13.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0052] Embodiment 1

[0053]FIG. 3A is an exploded perspective view of a waveguide couplershowing a first embodiment of the present invention. FIG. 3B is asectional view of the waveguide coupler. In the FIGS., 1 a and 1 bindicate dielectric substrates, 2 a and 2 b, indicate waveguideterminals formed in the dielectric substrates, 7 indicates solderserving as an electrically conductive joint member, and 8 a and 8 bindicate GND (grounded conductive) surfaces, each disposed on thesurface of the individual substrate for conducting electricity to thegrounded conductor of respective waveguide terminal.

[0054] The connection of the waveguide terminals will be described. Inthe figures, each dielectric substrate 1 a, 1 b includes the waveguideterminal 2 a, 2 b, formed in each substrate, and the GND surface 8 a, 8b disposed on the surface of the substrate for conducting electricity tothe grounded conductor of the waveguide terminal 2 a, 2 b. The twodielectric substrates 1 a and 1 b are arranged so that the GND surfaces8 a and 8 b oppose each other. The solder 7 is disposed between and incontact with the GND surfaces 8 a and 8 b, so as to surround thecircumference of the waveguide terminals 2 a and 2 b. Thus, the twodielectric substrates 1 a and 1 b are soldered to connect between thewaveguide terminals.

[0055] Forming the dielectric substrates 1 a and 1 b shown in FIGS. 3Aand 3B by multi-layered dielectric substrates can provide a similarconfiguration.

[0056] By connecting between the waveguide terminals formed in thedielectric substrates by soldering, it is possible to simplify theconnecting process of the waveguide terminals which has conventionallybeen fastened manually with screws. It is also possible to reduce thecost, because there is no need to use expensive parts, such as awaveguide adapter and carriers.

[0057] Embodiment 2

[0058]FIG. 4 is an exploded perspective view of a waveguide couplershowing a second embodiment of the present invention. FIG. 5A is a topview of the dielectric substrate which forms the waveguide coupler ofthe this embodiment, wherein a rectangular hole is formed in thedielectric substrate as a waveguide terminal. FIG. 5B is a verticalsectional view of the waveguide coupler formed by using the dielectricsubstrate shown in FIG. 5A. FIG. 6A is a top view of another example ofthe dielectric substrate which forms the waveguide coupler of thisembodiment, wherein the waveguide terminal is formed by through holesarranged in a rectangular shape. FIG. 6B is a vertical sectional view ofthe waveguide coupler formed by using the dielectric substrate shown inFIG. 6A. In these FIGS., 1 a, 1 b, 2 a, 2 b, 8 a, and 8 b indicate theelements similar to those shown in Embodiment 1, while 7 indicates aball-shaped, barrel-shaped or cylindrical solder, and 9 a and 9 bindicate through holes.

[0059] The connection of the waveguide terminals will be described. Inthe figures, the dielectric substrates 1 a and 1 b, the waveguideterminals 2 a and 2 b, and the GND surfaces 8 a and 8 b are arrangedsimilarly to those of Embodiment 1 and have similar functions. It shouldbe noted that the GND surface 8 a, although not shown in FIG. 4, isdisposed on the side of the dielectric substrate 1 a facing thedielectric substrate 1 b. A plurality of ball-shaped, barrel-shaped, orcylindrical solders 7 are arranged between and in contact with the GNDsurfaces 8 a and 8 b, so as to surround the circumference of thewaveguide terminals 2 a and 2 b. The ball-shaped, barrel-shaped, orcylindrical solders 7 are arranged in a row so that a gap betweenadjacent solders 7 is less than ¼ of the wavelength of a high frequencysignal which passes through the waveguide terminals 2 a and 2 b. In thisway, the two dielectric substrates 1 a and 1 b, and the ball-shaped,barrel-shaped, or cylindrical solders 7 are arranged so that thewaveguide terminals 2 a and 2 b, formed in the dielectric substrates 1 aand 1 b are connected by soldering.

[0060]FIG. 5A is a top view of the dielectric substrate of the waveguidecoupler described in connection with FIG. 4. In the configuration shownin FIG. 5A, each dielectric substrate 1 a, 1 b includes the waveguideterminal 2 a, 2 b formed in each substrate, and the GND surface 8 a, 8 bdisposed on the surface of the substrate for conducting electricity tothe grounded conductor of the waveguide terminal 2 a, 2 b. A pluralityof ball-shaped, barrel-shaped, or cylindrical solders 7 are arranged ina row on the GND surfaces 8 a and 8 b of the dielectric substrates 1 aand 1 b, respectively, around the waveguide terminals 2 a and 2 b. Inthis case, a gap between adjacent ball-shaped, barrel-shaped, orcylindrical solders 7 is less than ¼ of the wavelength of a highfrequency signal which passes through the waveguide terminals 2 a and 2b, as described above.

[0061] The waveguide terminals 2 a and 2 b can also be formed byarranging the through holes 9 a, 9 b in a rectangular shape, as in thedielectric substrates 1 a and 1 b shown in FIG. 6A, and disposing theGND surfaces 8 a, 8 b so as to conduct electricity to the through holes9 a, 9 b, in order to provide a waveguide coupler similar to that ofFIG. 4.

[0062] Moreover, the waveguide coupler similar to that of FIG. 4 canalso be provided by forming the dielectric substrates 1 a and 1 b shownin FIGS. 5A, 5B, 6A, and 6B by multi-layered substrates.

[0063] By connecting between the waveguide terminals formed in thedielectric substrate by soldering, it is possible to simplify theconnecting process of the waveguide terminals which has conventionallybeen fastened manually with screws. It is also possible to reduce thecost, because there is no need to use expensive parts, such as awaveguide adapter or carriers.

[0064]FIG. 7 is a vertical section of a model of a high frequency devicewhich uses the waveguide coupler according to the present invention. Thearchitecture of the device is such that the waveguide coupler of theabove embodiment having the dielectric substrates 1 a, 1 b is fixedinside a container 20. A high frequency circuit operable in themillimeter-wave band is mounted on the top surface of the dielectricsubstrate 1 a. The GND surface 8 a of the waveguide terminal 2 a of thedielectric substrate 1 a is bonded by solder 7 a to the GND surface 8 bof the waveguide terminal 2 b of the dielectric substrate 1 b. Thesolder 7 a is arranged to surround the waveguide terminals 2 a, 2 b, asmentioned above. The container 20 is made of metal and includes thewaveguide terminal 2 c formed opposite to the waveguide terminal 2 b.The dielectric substrate 1 b is fixed to the container 20 with anadhesive or screws. Through the layered waveguide terminals 2 a, 2 b,and 2 c of the dielectric substrates 1 a, 1 b, and the container 20,respectively, high frequencies are input/output between the highfrequency circuit on the dielectric substrate 1 a and the outside of thecontainer 20.

[0065] An electrical signal may be transmitted via a conductor betweenthe high frequency circuit on the dielectric substrate 1 a and theexternal circuit. The signal can be transmitted via an electrode 22 aexposed on the back side of the dielectric substrate 1 a via a throughhole formed therein, an electrode 22 b disposed on the surface of thedielectric substrate 1 b, and the solder 7 b for connecting betweenthese electrodes 22 a, 22 b. In this way, there is no need to connectwires to the top surface of the dielectric substrate 1 a by bonding orother means. As a result, an electric terminal connecting to the highfrequency circuit on the dielectric substrate 1 a can be taken out onthe dielectric substrate 1 b during the process of forming the waveguidecoupler by placing the dielectric substrate 1 a and 1 b in anoverlapping manner.

[0066] The high frequency circuit mounted on the dielectric substrate 1a is sealed in an airtight manner to prevent degradation of circuitcharacteristics. A glass epoxy substrate which is generally used forthis purpose is not suitable herein, because it absorbs water. Instead,a ceramic-based substrate is used for the dielectric substrate 1 a,which is suitable for the airtight sealing without causing the aboveproblem. The container 20 is made of metal, as mentioned above, andgenerally has a different coefficient of thermal expansion from that ofthe dielectric substrate 1 a. In general, the ceramic-based materialforming the dielectric substrate 1 a can crack easily. It is, therefore,not desirable for the container 20 to have a coefficient of thermalexpansion largely different from that of the dielectric substrate 1 a,because of the risk of physical failure, such as cracking, of thedielectric substrate 1 a.

[0067] To solve this problem, the metallic material forming thecontainer 20 may be selected to have a coefficient of thermal expansionsufficiently similar to that of the ceramic material 20 forming thedielectric substrate 1 a. At the same time, the coefficient of thermalexpansion of the dielectric substrate 1 b disposed between the container20 and the dielectric substrate 1 a is set to assume an intermediatevalue between the coefficients of the dielectric substrate 1 a and thecontainer 20. Specifically, the materials of the dielectric substrate 1a, the dielectric substrate 1 b, and the container 20 are selected sothat the magnitude of the coefficient of thermal expansion changes inthis order. For example, the container 20 made of metal usually exhibitsa greater thermal expansion than does the dielectric substrate 1 b. Insuch a device, if the dielectric substrate 1 b is attached to one sideof the container 20, the thermal expansion of this side of the container20 is reduced, alleviating the influence of thermal expansion of thecontainer 20 on the dielectric substrate 1 a. The dielectric substrates1 a and 1 b are connected at point contacts by the solders 7 a, 7 b, andboth the solders 7 a, 7 b themselves and the soldered connection betweenthe solders 7 a, 7 b and individual dielectric substrates are relativelyelastic. Therefore, different distortions due to thermal expansion ofthe dielectric substrates 1 a and 1 b can be absorbed at this part toreduce the stress within the dielectric substrate 1 a.

[0068] For example, if the dielectric substrate 1 a is made of aceramic-based material, and the container 20 is made of aluminum (Al),the dielectric substrate 1 b can be formed by a glass epoxy substrate.

[0069] In order to seal the waveguide terminals airtightly as in theabove device, it is preferable to use the configuration as shown in FIG.6A wherein the waveguide terminal 2 a is formed by the through holes 9 aarranged in a rectangular shape, rather than the configuration of FIG.5A having the waveguide terminal 2 a formed by a large aperture. In theconfiguration shown in FIG. 6A, the dielectric substrate remains insidethe enclosure of the through holes 9 a, and the through holes 9 a can beclosed easily by filling metals. By thus closing the waveguide terminal2 a, it can prevent flow of materials through it, while transmittinghigh frequency waves.

[0070] The above-described second embodiment illustrates one aspect ofthe present invention, wherein a plurality of electrically conductivejoint members are arranged to surround the waveguide terminals of bothdielectric substrates, and both dielectric substrates are bondedtogether by the multiple electrically conductive joint members which aresandwiched between the waveguide terminals of both dielectricsubstrates. With this configuration, the waveguide coupler can absorbthe difference of coefficients, for example, of thermal expansionbetween both dielectric substrates without causing any damage to thetransfer characteristic of high frequency waves. That is, stress isunlikely to result in the first dielectric substrate by distortion dueto thermal expansion or the like of the second dielectric substrate,preventing a crack or the like of the first dielectric substrate.

[0071] The above-described second embodiment also illustrates anotheraspect of the present invention, wherein a gap between adjacentelectrically conductive joint member is equal to, or less than ¼ of thewavelength of the high frequency signal passing through the waveguideterminal. With this configuration, it is possible to keep a goodtransfer characteristic of high frequency waves at the waveguidecoupler.

[0072] Embodiment 3

[0073]FIGS. 8A and 8B are top views of a dielectric substrate of awaveguide coupler according to a third embodiment of the presentinvention. In the FIGS., 1 to 9 indicate elements similar to those ofEmbodiment 2. 71 indicates a first solder row formed by the ball-shaped,barrel-shaped, or cylindrical solders 7 arranged in a row in parallelwith shorter sides of the waveguide terminal 2, and 72 indicates asecond solder row formed by the ball-shaped, barrel-shaped, orcylindrical solders 7 arranged in a row in parallel with longer sides ofthe waveguide terminal 2.

[0074]FIG. 9 is a graph showing the loss in the waveguide coupler. Thegraph represents the characteristic of transfer efficiency when L1 isfixed and L2 is changed, where L1 is a distance between the two firstsolder rows 71 arranged opposite to each other across the waveguideterminal 2, and L2 is a distance from an edge of the waveguide terminal2 to either one of the two second solder rows 72 arranged opposite toeach other across the waveguide terminal 2.

[0075] In FIG. 8A, the dielectric substrate 1 includes the waveguideterminal 2 formed therein, and the GND surface 8 disposed on the surfaceof the substrate for conducting electricity to the grounded conductor ofthe waveguide terminal 2. The multiple ball-shaped, barrel-shaped, orcylindrical solders 7 are arranged in a row around the waveguideterminal 2 on the GND surface 8 of the dielectric substrate 1. Herein, agap between adjacent ball-shaped, barrel-shaped, or cylindrical solders7 is set to be equal to, or less than ¼ of the wavelength of a highfrequency signal passing through the waveguide terminal 2. Assuming thatL1 is a distance between the two first solder rows 71 arranged oppositeto each other across the waveguide terminal 2, and L2 is a distance froman edge of the waveguide terminal 2 to either one of the two secondsolder rows 72 arranged opposite to each other across the waveguideterminal 2, L1 and L2 are set to have a relationship λ×(0.7 to1.3)=2/(1/L1 ²+1/L2 ²)^(½) with respect to the wavelength λ of a highfrequency signal passing through the waveguide terminal 2.

[0076] The transfer characteristic of the waveguide coupler will bedescribed. As shown in FIG. 9, when the distance L2 is changed with thedistance L1 being fixed, the loss in the waveguide coupler changessignificantly. The loss is minimized at the optimal L2 indicated in thefigure, The optimal L2 of this graph can be determined from the aboveexpression λ×(0.7 to 1.3)=2/(1/L1 ²+1/L2 ²)^(e,fra 1/2).

[0077] By setting L1 and L2 as above, it is possible to minimize theloss (and maximize the amount of transfer) in the waveguide coupler,while simplifying and reducing the cost of the connecting process of thewaveguide terminals.

[0078] A similar advantage can be provided by forming the waveguideterminal 2 by the through holes 9 arranged in a rectangular shape in thedielectric substrate, and disposing the GND surface 8 so as to conductelectricity to the through holes 9, as shown in FIG. 8b.

[0079] Forming the dielectric substrate 1 as shown in FIGS. 8A and 8B bya multi-layered dielectric substrate can also provide a similaradvantage.

[0080] Although the solders 7 described above are ball-shaped,barrel-shaped, or cylindrical, solders in other shapes, such as a plate,can provide similar advantages.

[0081] To summarize, in a further aspect of the present invention, themultiple electrically conductive joint members are arranged in a row onthe circumference of a rectangle having four sides, each two sides beingin parallel with either longer or shorter sides of the rectangularwaveguide terminal. Assuming that L1 is a distance between the firstrows of the conductive joint members arranged on opposite two sides ofthe rectangle running in parallel with the shorter sides of thewaveguide terminal, and L2 is a distance between the edge of thewaveguide terminal and either one of the second rows of the conductivejoint members arranged on opposite two sides of the rectangle running inparallel with the longer sides of the waveguide terminal, L1 and L2 areset to satisfy the relationship

λ×(0.7 to 1.3)=2/(1 /L1 ²+1/L2 ²)^(½)

[0082] where λ is the wavelength of a high frequency signal passingthrough the waveguide terminal. With this configuration, the loss in thewaveguide coupler is minimized, as described above.

[0083] It is understood from FIG. 9 that the loss in the waveguidecoupler becomes minimal at the optimal L2 and also at L2=0.Specifically, to correspond to L2=0, the first solder rows 71 and thesecond solder rows 72 can be arranged in close proximity to the edge ofthe waveguide terminal 2 (e.g., L2=0.2 to 0.5 mm), in order to minimizethe loss in the waveguide coupler. By arranging the solder rows closerto the edge of the waveguide terminal 2, an area of the dielectricsubstrates 1 a, 1 b to be occupied by the waveguide terminals surroundedby the solder rows is decreased. Accordingly, the size of the dielectricsubstrates 1 a, 1 b can be decreased, leading to cost reduction. This isparticularly advantageous when the dielectric substrate 1 a or 1 b isformed by a ceramic-based material, because such material is relativelyexpensive. In practice, when the waveguide coupler formed by thedielectric substrates 1 a, 1 b is used in a device, stress may result inthe dielectric substrates because of the difference of thermal expansionbetween the substrates and the container or the like to which thesubstrates are attached. When the thickness of the dielectric substratesis fixed, the dielectric substrates become stronger as the area of thesubstrates is smaller. Therefore, by using the above-describedarrangement of the solder rows to decrease areas of the dielectricsubstrates, it is possible to prevent cracking of the ceramic substrateas a result of thermal expansion or the like, to thereby improve thereliability of the device.

[0084] Thus, in a still further aspect of the present invention, themultiple conductive joint members are arranged in a row on thecircumference of a rectangle having four sides, each two sides being inparallel with longer or shorter sides of the rectangular waveguideterminal. Herein, both a distance between the first rows of theconductive joint members arranged on opposite two sides of the rectanglerunning in parallel with the shorter sides of the waveguide terminal,and a distance between the edge of the waveguide terminal and either oneof the second rows of the conductive joint members arranged on oppositetwo sides of the rectangle running in parallel with the longer sides ofthe waveguide terminal are set to be equal to, or less than 0.5 mm,respectively. This configuration is advantageous in terms of minimizingthe loss in the waveguide coupler, for example.

[0085] Embodiment 4

[0086]FIG. 10A is a top view showing a dielectric substrate of thewaveguide coupler according to a fourth embodiment of the presentinvention. FIGS. 10B and 10C are vertical sections of the dielectricsubstrate. In the figures, components 1 to 9 are similar to those ofEmbodiment 3,10 indicates a solder resist serving as a resist film forjoint members, 11 indicates a pad which forms part of the GND surface 8for disposing the ball-shaped, barrel-shaped, or cylindrical solders 7thereon, and 12 indicates a GND pattern formed in an internal layer of amulti-layered substrate.

[0087]FIG. 10A is a top view of the dielectric substrate 1, FIG. 10B isa vertical section of a single-layered dielectric substrate 1, and FIG.10C is a vertical section of a multi-layered dielectric substrate 1. InFIGS. 10A and 10B, the dielectric substrate 1 includes the waveguideterminal 2 formed therein, and the GND surface 8 disposed on the surfaceof the substrate for conducting electricity to the grounded conductor ofthe waveguide terminal 2. The solder resist 10 is applied on a region ofthe GND surface 8 other than the regions where the pads 11 used fordisposing the ball-shaped, barrel-shaped, or cylindrical solder 7 are tobe formed. Then, the pads 11 to which the ball-shaped, barrel-shaped, orcylindrical solder 7 can be attached are formed on this region of theGND surface 8.

[0088]FIG. 10C shows the dielectric substrate 1 of FIG. 10A formed by amulti-layered substrate, wherein the GND surface 8 is connected to thegrounded conductor of the waveguide terminal 2 via the GND pattern 12formed in the internal layer of the dielectric substrate 1 and thethrough hole 9. The solder resist 10 and the pads 11 used for disposingthe ball-shaped, barrel-shaped, or cylindrical solders 7 are provided asshown in FIG. 10A.

[0089] By providing the pads 11 for the ball-shaped, barrel-shaped, orcylindrical solders 7 using the solder resist 10, it is possible to setthe positions of the ball-shaped, barrel-shaped, or cylindrical solders7 accurately, while simplifying and reducing the cost of the connectingprocess of the waveguide terminal 2, as in Embodiment 2. It is alsopossible to minimize the loss in the waveguide coupler by deriving andsetting the parameters L1 and L2 concerning the positions of theball-shaped, barrel-shaped, or cylindrical solders 7, as in Embodiment3.

[0090] A similar advantage can be provided by forming the waveguideterminal by arranging the through holes in a rectangular shape on thedielectric substrate 1, and then disposing the GND surface 8 so as toconduct electricity to the through holes.

[0091] Although the solders 7 described above are ball-shaped,barrel-shaped, or cylindrical, solders in other shapes, such as a plate,can provide similar advantages.

[0092] If the solder resist 10 is not applied between the solders 7 onthe surface of the substrate with only a small gap being providedbetween individual solders, heat during bonding of the dielectricsubstrates 1 a, 1 b, could melt the solder such that it spreads over thesurface of the substrate, possibly merging and becoming a mass ofsolder. In principle, this happens between two adjacent solders 7.Therefore, a gap between the adjacent solders 7 is substantiallyeliminated, while a gap between the merged solder pair and its adjacentsolder 7 becomes larger than a designed value, leaving uneven gapsbetween solders.

[0093] In contrast, when the solder resist 10 is applied between thepositions where the solders 7 are to be placed according to thisembodiment, the solders 7 can be separated clearly from each other evenwhen only a small gap is provided between adjacent solders 7, therebymaking it easy to maintain a constant gap between the solders 7.Specifically, in the waveguide coupler compatible with higherfrequencies, it is easy to set the gap between the solders 7 to acertain design value, such as ¼ of the wavelength, to reduce the loss ofthe high frequency signal.

[0094] Thus, the fourth embodiment defines a still further aspect of thepresent invention, wherein at least one dielectric substrate includes agrounded conductive surface formed on the side of the substrate oppositeto the other dielectric substrate for conducting electricity to thegrounded conductor of the waveguide terminal, and a resist film for thejoint members formed on the grounded to conductive surface forpreventing attachment of the conductive joint members. In this way, thecontact regions are provided in part of the grounded conductive surface,while the resist film for the joint members is formed in a patternhaving apertures for the contact regions. By providing the resist filmfor the joint members on the surface of the grounded conductor of thedielectric substrate so as to expose multiple contact regions on whichthe conductive joint members are to be placed, it is possible to improveaccuracy of positioning of the conductive joint members, especially theaccuracy of spacing between adjacent conductive joint members, andthereby reduce loss in the waveguide coupler.

[0095] With the above configuration, it is also possible to suppressloss in the waveguide coupler by setting the positional relationshipbetween the waveguide terminal and the solder rows arranged on thecircumference of a rectangle, as in the third embodiment describedabove. For example, if it is desired to position the solder rows and theedge of the waveguide terminal in close proximity to each other, aregion covered by the solder resist 10 is provided between the edge ofthe wave guide terminal and the pads 11. In such a device, although itis not possible to eliminate a space between the solder rows and thewaveguide terminal, this distance can be reduced to 0.5 mm or less usingvarious patterning techniques. This facilitates achievement of apreferable transfer characteristic.

[0096] Embodiment 5

[0097]FIG. 11A is a top view showing a dielectric substrate of thewaveguide coupler according to a fifth embodiment of the presentinvention. FIG. 11B is a vertical section of the dielectric substrate.In the figures, components 11 and 12 are similar to those of Embodiment4.

[0098] The dielectric substrate1 includes the waveguide terminal 2formed therein, and the GND surface 8 disposed on the substrate forconducting electricity to the grounded conductor of the waveguideterminal 2. The GND pattern 12 connected to the grounded conductor ofthe waveguide terminal 2 is formed in the internal layer of thedielectric substrate 1 and connected to the pads 11 for the ball-shaped,barrel-shaped, or cylindrical solders 7 via the through holes 9.

[0099] By providing the pads 11 connected to the grounded conductor ofthe waveguide terminal 2 through the internal layer of the multi-layeredsubstrate, it is possible to set the positions of the ball-shaped,barrel-shaped, or cylindrical solders 7 accurately, while simplifyingand reducing the cost of the connecting process of the waveguideterminal, as in Embodiment 2. It is also possible, as in Embodiment 3,to minimize the loss in the waveguide coupler by deriving and settingthe parameters L1 and L2 concerning the positions of the ball-shaped,barrel-shaped, or cylindrical solders 7.

[0100] A similar advantage can be obtained by forming the waveguideterminal in the dielectric substrate 1 by arranging the through holes ina rectangular shape, and disposing the GND pattern 12 of the internallayer which conducts electricity to the through holes, the through holes9, and the pads 11.

[0101] Although the solders 7 described above are ball-shaped,barrel-shaped, or cylindrical, solders in other shapes, such as a plate,can provide similar advantages.

[0102] Thus, the fifth embodiment defines a still further aspect of thepresent invention, wherein at least one dielectric substrate ismulti-layered, and includes a plurality of pads serving as contactregions which are formed on the surface of the dielectric substrate forconducting electricity to the grounded conductor of the waveguideterminal through the internal layer and the through holes of thedielectric substrate. With this configuration, the multiple pads fordisposing the conductive joint members thereon are placed on the surfaceof the dielectric substrate at positions separated from the groundedconductive surface conducting electricity to the grounded conductor ofthe waveguide terminal. The pads are configured to conduct electricityto the grounded conductor of the waveguide terminal through the internallayer and the through holes of the multi-layered dielectric substrate.Thus, an accuracy of positioning the conductive joint members can beimproved and, accordingly, the loss in the waveguide terminal isreduced.

[0103] Embodiment 6

[0104]FIG. 12A is a top view showing a dielectric substrate of thewaveguide terminal according to a sixth embodiment of the presentinvention. FIGS. 12B and 12C are vertical sections of the dielectricsubstrate. In the figures, components 1 to 12 are similar to those ofEmbodiment 5, and 13 indicates a connecting wire for connecting the GNDsurface 8 to the pads 11.

[0105]FIG. 12A is a top view of the dielectric substrate 1, FIG. 12B isa vertical section of a single-layered dielectric substrate 1, and FIG.12C is a vertical section of a multi-layered dielectric substrate 1.

[0106] In FIGS. 12A and 12B, the dielectric substrate 1 includes thewaveguide terminal 2 formed therein, and the GND surface 8 disposed onthe surface of the substrate for conducting electricity to the groundedconductor of the waveguide terminal 2. The GND surface 8 is connected tothe pads 11 for the ball-shaped, barrel-shaped, or cylindrical solders 7via the connecting wire 13. The connecting wire 13 also connects betweenthe multiple pads 11. With this configuration, it is possible to preventthe flow of solder into the GND surface 8 when the connecting wire 13has a narrower width.

[0107]FIG. 12C shows a dielectric substrate 1 formed of a multi-layeredsubstrate, wherein the GND surface 8 is connected to the groundedconductor of the waveguide terminal 2 via the GND pattern 12 formed inthe internal layer of the dielectric substrate 1 and the through hole 9.The connecting wire 13 and the pads 11 are formed as shown in FIG. 12Aand have similar functions.

[0108] By providing the pads 11 connected to the grounded conductor ofthe waveguide terminal 2 via the connecting wire 13, it is possible toset the positions of the ball-shaped, barrel-shaped, or cylindricalsolders 7 accurately, while simplifying and reducing the cost of theconnecting process of the waveguide terminal, as in Embodiment 2. It isalso possible to minimize the loss in the waveguide coupler by derivingand setting the parameters L1 and L2 concerning the positions of theball-shaped, barrel-shaped, or cylindrical solders 7 as in Embodiment 3.

[0109] A similar advantage can be provided by forming the waveguideterminal such that the through holes are arranged in a rectangular shapein the dielectric substrate 1 and that the GND surface 8 conductselectricity to the through holes, the connecting wire 13, and the pads11.

[0110] Although the solders 7 described above are ball-shaped,barrel-shaped, or cylindrical, solders in other shapes, such as a plate,can provide similar advantages.

[0111] Thus, the sixth embodiment defines a still further aspect of thepresent invention, wherein at least one dielectric substrate includesthe grounded conductive surface formed on the side of the substrateopposite to the other dielectric substrate for conducting electricity tothe grounded conductor of the waveguide terminal, multiple pads formedon the same side of the substrate as the grounded conductive surface forserving as contact regions, and the connecting wire for electricallyconnecting each pad to the grounded conductive surface. With such aconfiguration, the multiple pads are disposed on the surface of thedielectric substrate at positions separated from the grounded conductivesurface conducing electricity to the grounded conductor of the waveguideterminal, and the connecting wire is provided for connecting the pads tothe grounded conductive surface. Thus, accuracy of positioning of theconductive joint members can be improved and, accordingly, the loss inthe waveguide coupler can be reduced.

[0112] Embodiment 7

[0113]FIG. 13A is a top view showing a dielectric substrate of thewaveguide coupler according to a seventh embodiment of the presentinvention. FIGS. 13B and 13C are vertical sections of the dielectricsubstrate. In the figures, components 1 to 12 are similar to those ofEmbodiment 4.

[0114]FIG. 13A is a top view of the dielectric substrate 1, FIG. 13B isa cross section of a single-layered dielectric substrate 1, and FIG. 13Cis a cross section of a multi-layered dielectric substrate 1. In FIGS.13A and 13B, the dielectric substrate 1 includes the waveguide terminal2 formed therein and the GND surface 8 disposed on the surface of thesubstrate for conducting electricity to the grounded conductor of thewaveguide terminal 2. The solder resist 10 is applied on a region of theGND surface 8 other than the regions where the pads 11 for disposing theball-shaped, barrel-shaped, or cylindrical solders 7 are to be formed.Thus, the pads 11 to which the ball-shaped, barrel-shaped, orcylindrical solders 7 can be attached are formed on this region of theGND surface 8. The pads 11 are oblong so that multiple solders 7 can bedisposed on one pad 11.

[0115]FIG. 13C shows the multi-layered dielectric substrate 1, whereinthe GND surface 8 is connected to the grounded conductor of thewaveguide terminal 2 via the GND pattern 12 formed in the internal layerof the dielectric substrate 1 and the through hole 9. The solder resist10 and the pads 11 for disposing the ball-shaped, barrel-shaped, orcylindrical solders 7 are formed as shown in FIG. 13A.

[0116] By using the solder resist 10 to provide the pads 11 for theball-shaped, barrel-shaped, or cylindrical solders 7, it is possible toset the positions of the ball-shaped, barrel-shaped, or cylindricalsolders 7 accurately, while, as in Embodiment 2, simplifying andreducing the cost of the connecting process of the waveguide terminals.It is also possible, as in Embodiment 3, to minimize the loss in thewaveguide coupler by deriving and setting the parameters L1 and L2concerning the positions of the ball-shaped, barrel-shaped, orcylindrical solders 7.

[0117] Although the pads 11 are oblong in the figures, pads 11 can beformed so as to surround the circumference of the waveguide 2 to providea similar advantage.

[0118] A similar advantage can also be provided even when adjacentball-shaped, barrel-shaped, or cylindrical solders 7 melt together andmerge after soldering.

[0119] Although the solders 7 described above are ball-shaped,barrel-shaped, or cylindrical, solders in other shapes, such as a plate,can provide similar advantages.

[0120] Also, a similar advantage can be provided by forming thewaveguide coupler by arranging the through holes in a rectangular shapein the dielectric substrate, and disposing the GND surface 8 so as toconduct electricity to the through holes.

[0121] Embodiment 8

[0122]FIG. 14A is a top view showing a dielectric substrate of thewaveguide coupler according to an eighth embodiment of the presentinvention. FIG. 14B is a vertical section of the dielectric substrate.In the FIGS., 1 to 11 are similar to those of Embodiment 4

[0123]FIG. 15 is a graph showing the coupling index of a high frequencysignal between the waveguide terminal shown in FIG. 14A and its adjacentwaveguide terminal. The adjacent waveguide terminal is disposed,although not shown, externally to the ball-shaped, barrel-shaped, orcylindrical solders 7 arranged in rows around the circumference of thewaveguide terminal shown in FIG. 14A.

[0124] The dielectric substrate 1 includes the waveguide terminal 2formed therein, and the GND surface 8 disposed on the surface of thesubstrate for conducting electricity to the grounded conductor of thewaveguide terminal 2. The solder resist 10 is applied on a region of theGND surface 8 other than the regions where the pads 11 for disposing theball-shaped, barrel-shaped, or cylindrical solders 7 are to be formed.Thus, the pads 11 for disposing the ball-shaped, barrel-shaped, orcylindrical solders 7 are formed on this region of the GND surface 8.Herein, the pads 11 are formed in double rows around and parallel withthe sides of the rectangular waveguide terminal 2 so as to provide tworows of the ball-shaped, barrel-shaped, or cylindrical solders 7.

[0125] In FIG. 15, a curve a represents the coupling index of a highfrequency signal between adjacent waveguide terminals when theball-shaped, barrel-shaped, or cylindrical solders 7 are arranged in asingle row around the waveguide terminal 2, while a curve b representsthe coupling index when the solders are arranged in double rows. Asindicated in the graph, by providing the ball-shaped, barrel-shaped, orcylindrical solders 7 in multiple rows, it is possible to suppress thecoupling index between adjacent waveguide terminals, which is especiallyadvantageous if, for example, more than one waveguide terminals 2 areprovided.

[0126] By providing the ball-shaped, barrel-shaped, or cylindricalsolders 7 in multiple rows, it is possible to suppress the couplingindex between adjacent waveguide terminals, while, as in Embodiment 4,setting the positions of the ball-shaped, barrel-shaped, or cylindricalsolders 7 accurately as well as simplifying and reducing the cost of theconnecting process of the waveguide terminal. It is also possible tominimize the loss in the waveguide coupler, as in Embodiment 3, byderiving and setting the parameters L1 and L2 concerning the positionsof the ball-shaped, barrel-shaped, or cylindrical solders 7.

[0127] A similar advantage can be provided by forming the waveguideterminal by arranging the through holes in a rectangular shape in thedielectric substrate 1, and disposing the GND surface 8 so as to conductelectricity to the through holes.

[0128] Although the solders 7 described above are ball-shaped,barrel-shaped, or cylindrical, solders in other shapes, such as a plate,can provide similar advantages.

[0129] Thus, the eighth embodiment defines a still another aspect of thepresent invention, wherein at least one dielectric substrate forming thewaveguide coupler includes multiple conductive joint members arranged inrows running parallel to the sides of the rectangular waveguideterminal, with several rows each being disposed for each side of thewaveguide terminal. With this configuration, it is possible to suppressthe coupling index between adjacent waveguide terminals.

[0130] Embodiment 9

[0131]FIG. 16A is a top view showing a dielectric substrate of thewaveguide coupler according to a ninth embodiment of the presentinvention. FIG. 16B is a vertical section of the dielectric substrate.In these figures, components 1 to 11 are similar to those of Embodiment8.

[0132]FIG. 17 is a graph showing the coupling index of a high frequencysignal between the waveguide terminal shown in FIG. 16A and its adjacentwaveguide terminal. Although not shown in the figure, the adjacentwaveguide terminal is disposedexternally to the ball-shaped,barrel-shaped, or cylindrical solders 7 arranged in rows around thewaveguide terminal 2 shown in FIG. 16A.

[0133] The dielectric substrate 1, the waveguide terminal 2, the GNDsurface 8, the solder resist 10, and the pads 11 are formed in a similarmanner to those of Embodiment 8. The pads 11 and the ball-shaped,barrel-shaped, or cylindrical solders 7 are formed in double rows aroundand parallel with the sides of the rectangular waveguide terminal 2,wherein a gap between the rows is set in the range of ±30% of the ¼wavelength of a high frequency signal (assuming its frequency to be F0)passing through the waveguide terminal 2.

[0134] In FIG. 17, a curve c represents the coupling index of a highfrequency signal between adjacent waveguide terminals when theball-shaped, barrel-shaped, or cylindrical solders 7 are arranged on thecircumference of the waveguide terminals in two rows with a certain gapprovided between them, while a curve d represents the coupling indexwhen the gap is set in the range of ±30% of the ¼ wavelength of a highfrequency signal (assuming its frequency to be F0) passing through thewaveguide terminal 2. By setting the gap between the ball-shaped,barrel-shaped, or cylindrical solders 7 in the range of ±30% of the ¼wavelength of the high frequency signal passing through the waveguideterminal 2, it is possible to further suppress the coupling indexbetween adjacent waveguide terminals only in the frequency band of thehigh frequency signal. This is advantageous when, for example, severalwaveguide terminals 2 are provided.

[0135] By arranging the ball-shaped, barrel-shaped, or cylindricalsolders 7 in several rows with a gap between the rows in the range of±30% of the ¼ wavelength of the high frequency signal passing throughthe waveguide terminal 2, it is possible to suppress the coupling indexbetween adjacent waveguide terminals, while, as in Embodiment 4, settingthe positions of the ball-shaped, barrel-shaped, or cylindrical solders7 accurately as well as simplifying and reducing the cost of theconnecting process of the waveguide terminals. It is also possible tominimize the loss in the waveguide coupler by deriving and setting theparameters L1 and L2 concerning the positions of the ball-shaped,barrel-shaped, or cylindrical solders 7.

[0136] A similar advantage can be provided by forming the waveguideterminal by arranging the through holes in a rectangular shape, anddisposing the GND surface 8 so as to conduct electricity to the throughholes.

[0137] Although the solders 7 are ball-shaped, barrel-shaped, orcylindrical in the above description, they can be in other shapes, suchas a plate, to provide a similar advantage.

[0138] Embodiment 10

[0139]FIG.18A is a top view of a dielectric substrate of the waveguidecoupler according to a tenth embodiment of the present invention. FIG.18B is a vertical section of the dielectric substrate. In the figures,components 1 to 11 are similar to those of Embodiment 4.

[0140] The dielectric substrate 1 includes two waveguide terminals 2formed therein, and the GND surface 8 disposed on the substrate forconducting electricity to the grounded conductors of the two waveguideterminals 2. The solder resist 10 is applied on a region of the GNDsurface 8 other than the regions where the pads 11 for disposing theball-shaped, barrel-shaped, or cylindrical solders 7 are to be formed.Thus, the pads 11 to which the ball-shaped, barrel-shaped, orcylindrical solders 7 can be attached are formed on this region of theGND surface 8. Herein, the pads 11 are also provided around and betweenthe two waveguide terminals.

[0141] By arranging more than one waveguide terminals 2 adjacent to eachother and disposing the ball-shaped, barrel-shaped, or cylindricalsolders 7 around and between the waveguide terminals 2, it is possibleto provide several waveguide terminals 2 in a small space, while settingthe positions of the ball-shaped, barrel-shaped, or cylindrical solders7 accurately as well as simplifying and reducing the cost of theconnecting process of the waveguide terminals as in Embodiment 4. It isalso possible, as in Embodiment 3, to minimize the loss in the waveguidecoupler by deriving and setting the parameters L1 and L2 concerning thepositions of the ball-shaped, barrel-shaped, or cylindrical solders 7.

[0142] A similar advantage can be provided by forming the waveguideterminals by arranging the through holes in a rectangular shape in thedielectric substrate 1, and disposing the GND surface 8 so as to conductelectricity to the through holes.

[0143] Although the solders 7 described above are ball-shaped,barrel-shaped, or cylindrical, solders in other shapes, such as a plate,can provide similar advantages.

[0144] Embodiment 10 defines a still further aspect of the presentinvention, wherein at least one dielectric substrate includes two ormore waveguide terminals formed therein, and the contact regions aredisposed on the circumference of each waveguide terminal so as tocorrespond to the opposing sides of adjacent rectangular waveguideterminals. Thus, the contact regions are shared by the adjacentwaveguide terminals. With this configuration, it is possible to provideseveral waveguide terminals in a small space.

[0145] Embodiment 11

[0146]FIGS. 19A and 19C are top views of two types of dielectricsubstrates of the waveguide coupler according to an eleventh embodimentof the present invention. FIG. 19B is a vertical section of thewaveguide coupler where the two types of dielectric substrates arejoined. In the figures, components 1 to 13 are similar to those ofEmbodiments 4 and 6.

[0147] The dielectric substrate 1 a is an upper substrate of the sectionshown in FIG. 19B, which includes the waveguide terminal 2 a formedtherein and the GND surface 8 a disposed on the surface of the substratefor conduct electricity to the grounded conductor of the waveguideterminal 2 a. The GND surface 8 a is connected via the connecting wire13 to the pads 11 a for the ball-shaped, barrel-shaped, or cylindricalsolders 7 disposed on the surface of the dielectric substrate 1 a. Theconnecting wire 13 also connects between the multiple pads 11. The GNDsurface 8 a is connected to the grounded conductor of the waveguideterminal 2 a via the GND pattern 12 formed in the internal layer of thedielectric substrate 1 a and the through holes 9.

[0148] The dielectric substrate 1 b is a lower substrate of the sectionshown in FIG. 19B, which includes the waveguide terminal 2 b formedtherein and the GND surface 8 b disposed on the substrate for conductingelectricity to the grounded conductor of the waveguide terminal 2 b. Thesolder resist 10 is applied on a region of the GND surface 8 b otherthan the regions where the pads 11 b for disposing the ball-shaped,barrel-shaped, or cylindrical solders 7 are to be formed. Thus, the pads11 b to which the ball-shaped, barrel-shaped, or cylindrical solders 7can be attached are formed on this region of the GND surface 8 b.

[0149] The two dielectric substrates 1 a and 1 b are disposed so thatthe pads 11 a and 11 b oppose each other. After that, the ball-shaped,barrel-shaped, or cylindrical solders 7 are provided to connect betweenthe waveguide terminals 2 a and 2 b by soldering.

[0150] With this configuration, it is possible to set the positions ofthe ball-shaped, barrel-shaped, or cylindrical solders 7 accurately,while, as in Embodiment 2, simplifying and reducing the cost of theconnecting process of the waveguide terminals. It is also possible, asin Embodiment 3, to reduce the loss in the waveguide coupler by derivingand setting the parameters L1 and L2 concerning the positions of theball-shaped, barrel-shaped, or cylindrical solders 7.

[0151] Although the solders 7 described above are ball-shaped,barrel-shaped, or cylindrical, solders in other shapes, such as a plate,can provide similar advantages.

[0152] Embodiment 12

[0153]FIG. 20A is an exploded perspective view of a waveguide coupleraccording to a twelfth embodiment of the present invention. FIG. 20B isa vertical section of the waveguide coupler. In the FIGS., 1 a, 1 b, 2a, 2 b, 8 a, and 8 c are similar to those of Embodiment 1, and 14indicates an electrically conductive adhesive.

[0154] The wave guide coupler will be described. In the figures, eachdielectric substrate 1 a, 1 b includes the waveguide terminal 2 a, 2 b,formed therein, and the GND surface 8 a, 8 b disposed on the surface ofthe substrate for conducting electricity to the grounded conductor ofthe waveguide terminal 2 a, 2 b. The two dielectric substrates 1 a and 1b are disposed in a manner that the GND surfaces 8 a and 8 b oppose eachother. The two dielectric substrates 1 a and 1 b are bonded together bythe conductive adhesive 14 sandwiched between the GND surfaces 8 a and 8b, whereby the waveguide terminals are connected. The conductiveadhesive 14 is disposed to surround the circumference of both waveguideterminals 2 a, 2 b.

[0155] A similar configuration can be realized by forming the dielectricsubstrates 1 a and 1 b shown in FIG. 20A of multi-layered substrates.

[0156] By bonding the waveguide terminals formed in the dielectricsubstrates with the electrically conductive adhesive, it is possible, asin Embodiment 1, to simplify the connecting process of the waveguideterminals, which has conventionally been manually fastened with screws.It is also possible to reduce the cost, because expensive parts, such asa waveguide adapter or carriers, may be eliminated.

[0157] Embodiment 13

[0158]FIG. 21A is an exploded perspective view of a waveguide coupleraccording to a thirteenth embodiment of the present invention. FIG. 21Bis a vertical section of the waveguide coupler. In the FIGS., 1 a, 1 b,2 a, 2 b, 8 a, and 8 c are similar to those of Embodiment 1, and 15indicates ball-shaped, barrel-shaped, or cylindrical pieces of metal.

[0159] The waveguide coupler will be described. In the figures, thedielectric substrates 1 a and 1 b, the waveguide terminals 2 a and 2 b,and the GND surfaces 8 a and 8 b are arranged similarly to those ofEmbodiment 1 and have similar functions. A plurality of ball-shaped,barrel-shaped, or cylindrical pieces of metal 15, such as gold, arearranged between the GND surfaces 8 a and 8 b so as to surround thecircumference of the waveguide terminals 2 a and 2 b. The ball-shaped,barrel-shaped, or cylindrical pieces of metal 15 are arranged in a rowin a manner that a gap between adjacent metal pieces 15 is equal to, orless than ¼ of the wavelength of a high frequency signal passing throughthe waveguide terminals 2 a and 2 b. When the two dielectric substrates1 a and 1 b are connected by thermocompression bonding, the waveguideterminals 2 a and 2 b, formed in the dielectric substrates 1 a and 1 bare joined via the metal pieces 15.

[0160] By connecting the waveguide terminals formed in the dielectricsubstrates by thermocompression bonding, it is possible, as inEmbodiment 1, to simplify the connecting process of the waveguideterminals, which has conventionally been fastened manually with screws.It is also possible to reduce the cost of the device because expensiveparts, such as a waveguide coupler or carriers, may be eliminated. Also,as in Embodiment 3, it is possible to minimize the loss in the waveguidecoupler by deriving and setting the parameters L1 and L2 concerning thepositions of the ball-shaped, barrel-shaped, or cylindrical metal pieces15.

[0161] Forming the dielectric substrates 1 a and 1 b of multi-layeredsubstrates can provide a similar advantage.

[0162] A similar advantage can also be provided by forming the waveguideterminals in the dielectric substrates by arranging the through holes ina rectangular shape, and disposing the GND surfaces 8 for conductingelectricity to the through holes.

[0163]FIG. 22 is a vertical section of a modified example of thisembodiment, wherein the waveguide coupler uses the dielectric substrates1 a, 1 b having the pads 11 formed by the solder resist 10 as shown inFIG. 10A. Herein, the solders 7 are fused to the pads 11 on which nosolder resist is applied.

What is claimed is:
 1. A waveguide coupler for connecting betweenrectangular waveguide terminals formed in two dielectric substratesarranged opposite to each other, wherein each of said dielectricsubstrates includes a contact region which conducts electricity to agrounded conductor of said waveguide terminal, one said contact regionbeing arranged to surround said waveguide terminal at a positionopposite to the other said contact region when both said waveguideterminals are connected together, and said dielectric substrates arejoined together with an electrically conductive joint member disposedbetween said opposing contact regions.
 2. The waveguide coupleraccording to claim 1, wherein a plurality of said electricallyconductive joint members are sandwiched between said dielectricsubstrates and arranged to surround said waveguide terminals.
 3. Thewaveguide coupler according to claim 1, wherein said electricallyconductive joint members are ball-shaped, barrel-shaped, or cylindrical.4. The waveguide coupler according to claim 2, wherein said twodielectric substrates have different coefficients of linear expansion.5. The waveguide coupler according to claim 2, wherein a gap betweenadjacent said electrically conductive joint members is equal to, or lessthan ¼ of the wavelength of a high frequency signal passing through saidwaveguide terminals.
 6. The waveguide coupler according to claim 5,wherein said multiple electrically conductive joint members are arrangedin a row on the circumference of a rectangle having four sides, eachside parallel to either longer or shorter sides of said rectangularwaveguide terminal, and a distance L1 and a distance L2 are determinedto satisfy a relationship λ×(0.7 to 1.3)=2/(1/L1 ²+1/L2 ²)^(½) whereinL1 is a distance between first rows of said electrically conductivejoint members disposed on opposing two sides of said rectangle runningin parallel with said shorter sides of said waveguide terminal, L2 is adistance between (said longer sides?) of said waveguide terminal andsecond rows of said electrically conductive joint members disposed onopposing two sides of said rectangle running in parallel with saidlonger sides of said waveguide terminal, and λ is a wavelength of thehigh frequency signal passing through said waveguide terminals.
 7. Thewaveguide coupler according to claim 5, wherein said multipleelectrically conductive joint members are arranged in a row on thecircumference of a rectangle having four sides, each side parallel toeither longer or shorter sides of said rectangular waveguide terminal,and it is determined that both a distance between said shorter sides ofsaid waveguide terminal and first rows of said electrically conductivejoint members disposed on opposing two sides of said rectangle runningin parallel with said shorter sides of said waveguide terminal, and adistance between said longer sides of said waveguide terminal and secondrows of said conductive joint members disposed on opposing two sides ofsaid rectangle running in parallel with said longer sides of saidwaveguide terminal are equal to, or less than 0.5 mm.
 8. The waveguidecoupler according to claim 1, wherein at least one among said dielectricsubstrates includes a grounded conductive surface formed on the surfaceof said substrate opposing the other said dielectric substrate forconducting electricity to the grounded conductor of said waveguideterminal, and a resist film for the joint members formed on saidgrounded conductive surface for preventing the attachment of saidelectrically conductive joint members, a region of said groundedconductive surface serves as said contact region, and said resist filmfor the joint members is formed in a pattern having an aperture for saidcontact region.
 9. The waveguide coupler according to claim 1, whereinat least one among said dielectric substrates is multi-layered andincludes a plurality of pads serving as said contact region, said padsbeing formed on the surface of said dielectric substrate for conductingelectricity to the grounded conductor of said waveguide terminal via aninternal layer of said dielectric substrate and a through hole.
 10. Thewaveguide coupler according to claim 1, wherein at least one among saiddielectric substrates comprises: a grounded conductive surface formed onthe surface of said dielectric substrate opposing the other saiddielectric substrate for conducting electricity to the groundedconductor of said waveguide terminal, a plurality of pads formed on thesame surface of said dielectric substrate as said grounded conductivesurface for serving as said contact region, and a connecting wire forelectrically connecting each of said pads to said grounded conductivesurface.
 11. The waveguide coupler according to claim 1, wherein saidcontact region of said at least one said dielectric substrate is dividedinto a plurality of regions surrounded by a solder resist, each regionbeing provided with a plurality of said multiple conducting jointmembers.
 12. The waveguide coupler according to claim 1, wherein said atleast one said dielectric substrate includes a plurality of saidelectrically conductive joint members arranged in rows parallel with aside of said rectangular waveguide terminal, with two or more rows beingallocated for each side.
 13. The waveguide coupler according to claim12, wherein a gap between said rows of said electrically conductivejoint members running in parallel with each side of said waveguideterminal is in the range of ±30% of ¼ of the wavelength of a highfrequency signal passing through said waveguide terminals.
 14. Thewaveguide coupler according to claim 1, wherein said at least one saiddielectric substrate includes two or more waveguide terminals formed insaid dielectric substrate, said contact region is arranged on thecircumference of each of said waveguide terminals so as to surround eachof said waveguide terminals, and said contact region formedcorresponding to opposing sides of adjacent said rectangular waveguideterminals is shared by said adjacent waveguide terminals.
 15. Thewaveguide coupler according to claim 1, wherein said electricallyconductive joint member is formed of solder and said two dielectricsubstrates are joined together by soldering.
 16. The waveguide coupleraccording to claim 1, wherein said electrically conductive joint memberis an electrically conductive adhesive.
 17. The waveguide coupleraccording to claim 1, wherein said electrically conductive joint memberis a metal or a material containing metal, and said two dielectricsubstrates are joined together by thermocompression bonding using saidmetal or said material containing metal.